Process for extraction of copper from arsenical copper sulfide concentrate

Abstract

A process for extraction of copper from an arsenical copper sulfide concentrate is provided. The process includes atmospheric oxidative leaching of a feed slurry including the arsenical copper sulfide concentrate and an acidic iron sulfate-containing leach solution, in the presence of oxygen, to produce a leach slurry including copper and arsenic dissolved into the leach solution. After dissolving the copper and arsenic, and before precipitating the arsenic dissolved during the oxidative leaching, pre-precipitation solids are recovered from the leach slurry to produce the pre-precipitation solids and a resulting pregnant leach solution including the copper and arsenic. Scorodite-containing seed is introduced to the pregnant leach solution including the copper and arsenic to induce precipitation of the arsenic dissolved during the oxidative leaching, as scorodite. Solids are recovered from the pregnant leach solution to produce the solids, including the scorodite, and an arsenic-reduced pregnant leach solution including the copper. The arsenic-reduced pregnant leach solution including the copper is subjected to solvent extraction for recovering copper and thereby producing a raffinate including sulfuric acid and iron sulfate, and at least a portion of the raffinate including the sulfuric acid and iron sulfate is recycled to the oxidative leaching.

The invention claimed is: 
     
       1. A process for extraction of copper from an arsenical copper sulfide concentrate, the process comprising:
 atmospheric oxidative leaching of a feed slurry including the arsenical copper sulfide concentrate and an acidic iron sulfate-containing leach solution, in the presence of oxygen to produce a leach slurry including copper and arsenic dissolved into the acidic iron sulfate-containing leach solution; 
 after dissolving the copper and arsenic, and before precipitating the arsenic dissolved during the oxidative leaching, recovering pre-precipitation solids from the leach slurry to produce the pre-precipitation solids and a resulting pregnant leach solution including the copper and arsenic; 
 introducing scorodite-containing seed to the pregnant leach solution including the copper and arsenic to induce precipitation of the arsenic dissolved during the oxidative leaching, as scorodite, providing a precipitation-induced pregnant leach solution; 
 recovering solids from the precipitation-induced pregnant leach solution to produce the solids, including the scorodite, and an arsenic-reduced pregnant leach solution including the copper; 
 subjecting the arsenic-reduced pregnant leach solution including the copper to solvent extraction for recovering copper and thereby producing a raffinate including sulfuric acid and iron sulfate; 
 recycling at least a portion of the raffinate including the sulfuric acid and iron sulfate to the oxidative leaching. 
 
     
     
       2. The process according to  claim 1 , wherein oxidative leaching is carried out at a temperature in a range of about 80° C. to about 95° C. 
     
     
       3. The process according to  claim 1 , wherein oxidative leaching and introducing scorodite are carried out at a temperature in a range of about 80° C. to about 95° C. 
     
     
       4. The process according to  claim 1 , wherein recovering solids from the precipitation-induced pregnant leach solution to produce the solids, including the scorodite, and the arsenic-reduced pregnant leach solution including the copper comprises subjecting the precipitation-induced pregnant leach solution to liquid/solid separation. 
     
     
       5. The process according to  claim 1 , wherein recovering solids from the precipitation-induced pregnant leach solution to produce the solids, including the scorodite, and the arsenic-reduced pregnant leach solution including the copper comprises subjecting the precipitation-induced pregnant leach solution to flotation. 
     
     
       6. The process according to  claim 1 , wherein the arsenical copper sulfide concentrate comprises pyrite and at least one of enargite, tennantite, and collusite. 
     
     
       7. The process according to  claim 1 , wherein the arsenical copper sulfide concentrate comprises about 15 to 30% by weight Cu, 15 to 30% by weight Fe, 5 to 12% by weight As, and 30 to 40% by weight total S. 
     
     
       8. The process according to  claim 1 , wherein introducing the scorodite-containing seed to the pregnant leach solution including the copper and arsenic to induce the precipitation of the arsenic and the precipitation of the arsenic are carried out without adjusting acid concentration before or during precipitation of the arsenic. 
     
     
       9. The process according to  claim 1 , wherein introducing the scorodite-containing seed to induce precipitation of arsenic is carried out after at least about 75% by weight of the copper is dissolved from the arsenical copper sulfide concentrate during atmospheric oxidative leaching. 
     
     
       10. The process according to  claim 9 , wherein introducing the scorodite-containing seed to induce precipitation of arsenic is carried out after at least about 95% by weight of the copper is dissolved from the arsenical copper sulfide concentrate during atmospheric oxidative leaching. 
     
     
       11. The process according to  claim 1 , wherein the raffinate provides sulfuric acid and iron ions to the leach solution. 
     
     
       12. The process according to  claim 11 , wherein recycling comprises recycling about 60 to about 90% by weight of the raffinate to the atmospheric oxidative leaching. 
     
     
       13. The process according to  claim 1 , wherein the acidic iron sulfate-containing leach solution contains chloride ions. 
     
     
       14. The process according to  claim 1 , wherein the recycling is a source of soluble iron in the acidic iron sulfate-containing leach solution. 
     
     
       15. The process according to  claim 1 , wherein a composition of the leach slurry is controlled by controlling an extent of oxidation during oxidative leaching to control sulfuric acid and soluble iron concentrations for copper dissolution and subsequent precipitation of arsenic as scorodite. 
     
     
       16. The process according to  claim 1 , wherein the acidic iron sulfate-containing leach solution has a ferric ion concentration of at least about 10 g/L. 
     
     
       17. The process according to  claim 1 , wherein the leach slurry has a ferric ion concentration in solution in the range of about 15 g/L to about 25 g/L prior to introducing scorodite-containing seed. 
     
     
       18. The process according to  claim 1 , wherein the acidic iron sulfate-containing leach solution has a sulfuric acid concentration of about 30 g/L to about 60 g/L. 
     
     
       19. The process according to  claim 1 , wherein an initial concentration of solids in the feed slurry is about 10% to about 30% by weight of solids prior to dissolution of copper and arsenic. 
     
     
       20. The process according to  claim 1 , wherein the leach slurry includes a carbonaceous catalyst. 
     
     
       21. The process according to  claim 1 , wherein oxidation of iron-containing minerals in the arsenical copper concentrate is controlled to achieve a molar ferric ion to arsenic ratio in solution of at least 1:1 prior to the precipitation of arsenic as scorodite. 
     
     
       22. The process according to  claim 21 , wherein oxidation of iron-containing minerals in the arsenical copper concentrate is controlled to achieve a ferric ion concentration in solution of about 15 g/L to about 25 g/L prior to the precipitation of arsenic as scorodite. 
     
     
       23. The process according to  claim 1 , wherein the arsenic is precipitated at a temperature of about 90° C. to about 95° C. 
     
     
       24. The process according to  claim 1 , wherein introducing scorodite-containing seed comprises introducing an amount of the scorodite-containing seed to provide an arsenic mass ratio of the arsenic in the scorodite seed material to the soluble arsenic in the pregnant leach solution including the copper and arsenic, in the range of about 3.5:1 to about 4.5:1. 
     
     
       25. The process according to  claim 1 , wherein introducing the scorodite-containing seed comprises recycling a portion of the solids, including the scorodite, to the pregnant leach solution including the copper and arsenic, to induce the precipitation of the arsenic dissolved during the oxidative leaching, as scorodite. 
     
     
       26. The process according to  claim 1 , wherein the scorodite-containing seed material is obtained by flotation of the precipitation-induced pregnant leach solution to produce a flotation concentrate and scorodite-rich flotation tailings. 
     
     
       27. The process according to  claim 1 , wherein recovering solids from the precipitation-induced pregnant leach solution, comprises subjecting the precipitation-induced pregnant leach solution, after precipitating the arsenic, to a flotation, without prior liquid/solid separation, to produce a flotation concentrate and scorodite-rich flotation tailings, wherein the scorodite-containing seed material comprises a portion of the flotation tailings. 
     
     
       28. The process according to  claim 1 , wherein recovering the pre-precipitation solids from the leach slurry comprises subjecting the leach slurry to liquid/solid separation. 
     
     
       29. The process according to  claim 28 , wherein the liquid/solid separation comprises thickening, filtration, or both. 
     
     
       30. The process according to  claim 28 , wherein the liquid/solid separation comprises washing at least some separated solids, and at least some produced washing liquor is combined with the pregnant leach solution including the copper and arsenic. 
     
     
       31. The process according to  claim 28 , wherein recovering pre-precipitation solids from the leach slurry removes at least 90 wt % of the solids present in the leach slurry. 
     
     
       32. The process according to  claim 31 , wherein recovering pre-precipitation solids from the leach slurry removes at least 95 wt % of the solids present in the leach slurry. 
     
     
       33. The process according to  claim 32 , wherein recovering pre-precipitation solids from the leach slurry removes at least 99 wt % of the solids present in the leach slurry. 
     
     
       34. The process according to  claim 33 , wherein recovering pre-precipitation solids from the leach slurry removes substantially all of the solids present in the leach slurry. 
     
     
       35. The process according to  claim 1 , wherein an amount of copper extracted during solvent extraction is about 95% by weight of the total copper content or greater. 
     
     
       36. The process according to  claim 1 , wherein the arsenical copper sulfide concentrate is ground prior to oxidative leaching. 
     
     
       37. The process according to  claim 36 , wherein the arsenical copper sulfide concentrate is ground to provide a particle size distribution P 80  of about 15 μm to about 25 μm.